The purpose of the proposed research is to use two photon tunable dye laser spectroscopy to identify in the visual chromophores and visual pigments the energy and photophysical characteristics of the "1Ag-"-like state, as well as other "forbidden" pi pi and sigma pi states. Solvent effect and pressure effect studies of the excitation bands will be used to help characterize the dipolar and dispersive properties of the observed electronic states. This information will be compared with the results of all valence electron SCF-MO-CID calculations optimized by the inclusion of high levels of double excitation configuration interaction. A portion of the research effect will be devoted to the development of a useful semiempirical all valence electron SCF-MO-CID formalism. The molecules to be spectroscopically and theoretically studied will include the all-trans, 9-cis, 11-cis and 13-cis isomers of retinol, retinal, the Schiff base of retinal and the protonated Schiff base of retinal as well as the visual pigment, rhodopsin. This investigation will afford the first detailed analysis of the location and conformational dependence of the low-lying "forbidden" levels in these compounds, and will help delineate their importance in the visual process.